rataling sound comin from the engine

Try removing the clutch and see what happens when you start the motor. Hopefully, that is the problem...

samkrut96 said:

Can I start the engine with the gearbox and clutch off?

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yes, of course you can start and run an engine without the gearbox.
you don't state what gearbox you are running.

Bell sound would be the centrifugal clutch bell ringing.....

samkrut96 said:

Can I start the engine with the gearbox and clutch off?

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I am assuming that you have a hoot gearbox. Just pull the out the big gear and unscrew the bolt that holds the clutch in place on the motor shaft.(I just put a screw driver in the flywheel to keep the engine from spinning when doing that), and then remove both the clutch bell and the clutch itself. You don't have to pull the gearbox off. The point of this is to determine if the sound is from your engine or in your gearbox/clutch assembly, ie, if it still makes the noise with the gearbox disengaged, the problem will be on the engine side.

I listened to your video. The good news is the engine is not seriously damaged.
The pull starter has malfuctioned. It sounds like one or both of the pawls is not retracting from the start reel, as seen in this parts diagram.
http://www.bicycle-engines.com/49cc-engine-parts-diagram.html

Part #48, start reel.
Unfortunately the diagram does not show the actual pull starter assembly.

There are guide channels that are supposed to operate the pawls. Remove the 3 nuts and the black plastic pull starter. There is no need to remove the red fan shroud / magneto cover. Be careful of the 3 metal spacers. They should stay in place inside the fan shroud holes but if they drop out don't loose them.You should be able to see the pawls in the center of the pull starter cover and perhaps what has gone wrong.
The pawls are L shaped metal bars located in the center plastic pawl carrier.

My thought is the large Philips head screw in the center that tensions the pull starter pawl carrier has come loose/ backed off a little and the guide assembly cannot operate correctly.
The center pawl carrier needs to have a little bit of rotational drag to it in order for the guide ramps to operate the pawls.

If the assembly is not repairable, Thatsdax sells a replacement pull starter at a reasonable price.
http://thatsdax.com/ENGINE_KIT_PARTS_PAGE_4.html

samkrut96 said:

I have a 49cc 4 stroke engine. I have bean having problems with my gear box and so I put the motorbike away for month until I found time to work on it. When I started it up yesterday it worked fine no problems than all of a sudden ther was a loud rattalng sound. Now every tme I start it there is a rattaling sound. If I pull the pull start slowy without starting it I hear the rattle sound. Itsound like sharp metal rattling. Almost like a a bell. Please help thank you

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Did you remove the valve cover and check the clearances?
Are the rocker arms rattling around?

I wouldn't run that motor anymore before you figure out what
the noise is because you are going to do more damage

Old trick is to use a screw driver like a stethoscope to isolate the noise.

The only other thing I can think of is the oil dipper on the crank is broken
and banging around.

sounds almost like rod knock.

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MotorBicycleRacing said:

Did you remove the valve cover and check the clearances?
Are the rocker arms rattling around?

I wouldn't run that motor anymore before you figure out what
the noise is because you are going to do more damage

Old trick is to use a screw driver like a stethoscope to isolate the noise.

The only other thing I can think of is the oil dipper on the crank is broken
and banging around.

Click to expand...